Method for the aftertreatment of paper or nonwoven fabrics made of incompletely regenerated viscose fibers

ABSTRACT

In the process of making a paper product from incompletely regenerated viscose fibers, a washing step which includes the disposing of the washing net below the regeneration net a given distance and establishing a ratio of net speeds within a specified range.

United States Patent [191 Aoki [451 Aug. 26, 1975 1 METHOD FOR THEAFTERTREATMENT OF PAPER OR NONWOVEN FABRICS MADE OF INCOMPLETELYREGENERATED VISCOSE FIBERS [75] Inventor: Yoshikazu Aoki, Otsu. Japan[73] Assignee: Tachikawa Research Institute,

Kyoto. Japan [22] Filed: Dec. 7, 1973 [21] App]. No; 214,969

[52] US. Cl -162/157 C; 8/152; 162/196 [51] Int. Cl. ..D21H 5/12 [58]Field of Search 162/157 C, 196; 264/181,

264/188, 195; 8/152, 156; 68/205 R, DIG. 5, 177, 178

[56] References Cited UNITED STATES PATENTS 3,320,117 5/1967 Aoki et a1162/157 C 3,608.10) 9/1971 Fleissner et a1 H 68/D1G. 5

Primary ExaminerS. Leon Bashore Assistant ExaminerWi11iam F Smith [57]ABSTRACT In the process of making a paper product from incompletelyregenerated viscose fibers, a washing step which includes the disposingof the washing net below the regeneration net at given distance andestablishing a ratio of net speeds within a specified range.

1' Claim, 2 Drawing Figures METHOD FOR THE AFT ERTREATMENT OF PAPER ORNONWOVEN FABRICS MADE OF INCOMPLETELY REGENERATED VISCOSE FIBERS Thisinvention relates to the method for the useful and continuousaftertreatment of the wet sheet made of incompletely regenerated viscosefibers.

Paper or nonwoven fabrics made of incompletely regenerated viscosefibers is already well known, i.e., US. Pat. No. 3,320,l l7 and US. Pat.No. 3,553,078. In these processes incompletely regenerated viscosefibers are, after cutting in a suitable length, dispersed into water anda wet sheet is formed on a paper machine from the slurry. The wet sheetthus obtained is regenerated completely on a regeneration net, and afterthat in order to obtain the desired paper or non woven fabric, the wetsheet must be aftertreated or washed before drying, as in theconventional manufacture of viscose fibers. Desulphurization andbleaching of the sheet is then performed in the usual manner.

Generally speaking, there are two ways of washing a sheet, the fibroussheet is washed successively on a washing net at the speed same as thatof the paper machine, or the sheet is washed in a free state same as inthe cellophane process. However, according to our experiments, it wasfound that these two methods are unsuitable to the treatment of thepresent wet sheet.

In the case ofa heavy sheet the washing method used in the conventionalcellophane process may be acceptable. However, in the treatment of alight sheet, the basic weight of which is less than 30 g/m difficultiesare presented. In such a light sheet, the sheet was apt to be brokenduring the processing and, moreover, both edges of the sheet being aptto have an inside curl or fold. These problems precluded a smoothoperation of the process.

On the other hand, if the running speed of the washing net is the sameas that of the regeneration net, i.e., the paper machine speed, theprocess is preformed efficiently. However, in this case, the washing netmust be dimensionally elongated in proportion to the increase in thepaper machine speed in order to accomplish the desired washing becausein this method, the washing net speed naturally must be increased withthe increasing of the paper machine speed. It is a problem from acommercial viewpoint to use such a long net in the washing process.

The present invention is a proposal for solving the above-mentionedproblems. It is no exaggeration to say that a successful washing methodfor a wet sheet formed of incompletely regenerated viscose fibers hasbeen smoothly accomplished by the present invention not withstanding thethickness of the wet sheets.

The present washing method is carried out originally by using a washingnet. The running speed of the net is set to a certain speed less thanthat of the regeneration net. Under such a condition the wet sheet isshaken off from the regeneration net to the washing net placing thesheet in the folded state.

A better understanding of the invention may be had from the followingdescription read in conjunction with the accompanying drawings, wherein:

FIG. I is a general view of the present washing method; and

FIG. 2 is an enlarged view showing the folded state of the sheet.

In FIG. I, the wet sheet 1 on the regeneration net 2 is shaken off ontothe washing net 4 keeping the folded state 3. Both nets are in the formof endless and porous or reticulated belts. In this case, the foldedstate of the sheet is determined by the speed ratio of both nets. Thefolded sheet is treated on the washing net by pouring the treatingliquors from the washing trays 5. The washed sheet is sent to a dryerafter being dehydrated by passing through press rolls 6, the speed ofthe dryer being the same as the speed of the paper machine.

In FIG. 2, the folded state of a sheet is shown. The fold in the sheetis a function of the speed ratio R of the washing net speed to theregeneration net speed and the distance A, the vertical distance betweenthe nets. The smaller the speed ratio R and the larger the verticaldistance A, the broader is the width B of the fold in the sheet.

According to our experiments, the value of R should be within the ratioUS to 1/50. When R is larger than l/3, the process loses its commercialvalue and when R is less than 1/50, the folded state of the sheet is notuniform and smooth operation is apt to be impaired.

On the other hand, the value of the vertical distance A should be setbetween 5 and 50. Only within such a range, is the uniform folding ofthe sheet possible.

After finishing the washing, the wet sheet is dehydrated after onceagain returning its running speed to the original speed, i.e., papermachine speed. In the present invention, the operation is smooth insofaras the folding of the sheet is uniformly effected. By adjust ing R tobetween H3 and 1/50 and A to between 5 and 50 cm, it is possible totreat the sheet perfectly with a comparatively short machine at a fairlyhigh speed.

EXAMPLE I After cutting in 10 mm length, incompletely regeneratedviscose fibers were dispersed in water. A wet sheet was formed on apaper making wire net from the slurry at the speed of 50 m/min. Afterpatterning the wet sheet, the sheet was regenerated completely on aregeneration net by pouring hot acid liquor containing 5 g/l ofsulphuric acid at the same speed as that of the paper machine. Aftershaking off the wet sheet on the washing net, the washing treatmentswere done at three running speeds, i.e., l5, 5 and L2 m/min.,respectively, for the washing net. In each case the vertical distancewas set to 25 cm. The desulphurization was performed by the liquorcontaining 3 g/l of caustic soda at the temperature of C, and thebleaching by the sodium hy pochlorite liquor containing 1 g/l ofavailable chlorine at the temperature of 20C.

In order to estimate the effect of the present treatment, the reduciblesulphur content of the product sheets was measured quantitatively. Theresults are shown in the following table.

It is clear from the Table that the effect of the present washing isconstant in the wide range of the speed ratio R.

3 4 What is claimed is: and bleaching treating liquors respectittly on awash- In a Process for manufacwl'lng P p OT nQnWOVCn ing net having arunning speed of from 1/3 to 1/50 of fabrics fmm incompletely reggnemtedSeuss fibers the speed of said regeneration net, the vertical distancewhich have been dispersed in water to form a slurry and subsequentlyformed into a wet sheet on a paper mak- 5 ing machine. completelyregenerating the fibers 0f the sheet on a regeneration net traveling thesame running speed as said paper making machine. the improvement eludingPress rolls having the Same running Speed comprising the steps ofdesulphurizing and bleaching regeneration the completely regeneratedsheet with desulphurizing 1n between the regeneration net and thewashing net being from 5 to 50 centimeters and drying the desulphurizedand bleached sheet in a drier. said drier in-

1. IN A PROCESS FOR MANUFACTURING PAPER OR NONWOVEN FABRICS FROMINCOMPLETELY REGENERATED VISCOSE FIBES WHICH HAVE BEEN DISPERSED INWATER TO FORM A SLURRY AND SUBSEQUENTLY FORMED INTO A WET SHEET ON APAPER MAKING MACHINE, COM PLETELY REGENERATING THE FIBERS ON THE SHEETON A REGENERATION NET TRAVELING THE SAME SPEED AS SAID PAPER MAKINGMACHINE, THE IMPROVEMENT COMPRISING THE STEPS OF DESULPHURIZING ANDBLEACHING THE COMPLETELY REGENERATED SHEET WITH DESULPHURIZING ANDBLEACHING TREATING LIQUORS RESPECTIVELY ON A WASHING NET HAVING ARUNNING SPEED OF FROM 1/3 TO 1/50 OF THE SPEED OF SAID REGENERATION NET,THE VERTICAL DISTANCE BETWEEN THE REGENERATION NET AND THE WASHING NETBEING FROM 5 TO 50 CENTIMETERS, AND DRYING THE DESULPHURIZED ANDBLEACHED SHEET IN A DRIER, SAID DRIER INCLUDING PRESS ROLLS HAVING THESAMD RUNNING SPEED AS SAID REGENERATION NET.